Web-tension sensing and control apparatus

ABSTRACT

A web-tension sensing and control apparatus for sensing and controlling the tension of the webs of feed rolls and webs of paper, plastic resinous films, and the like, fed from such rolls. Pneumatic sensing means senses the tension or slack in the web and actuates pneumatic braking means which brakes the action of the feed roll for the web and thus takes up the slack in the web.

[ June 17, 1975 United States Patent 1 Edes et al.

33 M4 55 MM 22 M44 222 4.. 2 m m t m au ubm uo DRM 56 667 999 NH 822 673766 .9 290 083 333 WEB-TENSION SENSING AND CONTROL APPARATUS [75]Inventors: Ferenc Edes, Bolingbrook; Henry L.

Glanataslo, River Forest, both of ill. Primary Examiner john w HuckfirtAir-Trol Systems, lnc., Addison, lll.

Dec. 26, 1973 Assislant Examiner-John M. Jillions [73] Assignee:

[22] Filed:

Attorney, Agent, or FirmCharles B Cannon Appl. No: 428,367

g and control apparatus for sensg and controlling the tension of thewebs of feed rolls and webs of paper, plastic resinous films, and thelike, fed from such rolls. Pneumatic sensing means .m S n e S n .m S n en b e w Am 383 405 35 27 Uh 3 45 26M W 7 "H2 4 W Wmh C H.r Ha e s 0 .mUhF HUN 555 [iii senses the tension or slack in the web and actuatespneumatic braking means which brakes the action of the feed roll for theweb and thus takes up the slack in the web.

S T N w M mm m mT S e D E W N U N 5 5 Claims, 21 Drawing Figures 333 555777 l// 222 444 222 m m n m en mko r r 0 a HPA 243 356 999 ill l// 0 8 95 811 1 0060 23 PATENTEDJUN 17 I975 SHEET PATENTEDJUN 17 1975PATENTEDJUN 17 ms 48 89 W fi PATENTEIJJUN1 7 ms SHEET WEB-TENSIONSENSING AND CONTROL APPARATUS OBJECTS An object of the invention is toprovide a new and improved web-tension sensing and control apparatus fortensioning a roll and web of paper, plastic resinous film, and the like,and for maintaining the proper and desired tension thereon.

Another object of the invention is to provide a new and improvedweb-tension sensing and control apparatus for tensioning a web of paper,plastic resinous film, and the like, which embodies, in combination,pneumatic sensing means which senses the relative tension or slack inthe web and actuates peumatic braking means to brake the rotation of thefeed roll for the web and thus increase the tension on the web and takeup the slack therein.

Another object of the invention is to provide a new and improvedweb-tension sensing and control apparatus in which the tension on theweb of paper, flexible plastic resinous film, or the like, may bepre-selected and the tension maintained constant as the roll unwinds andthe feed roll for the web becomes smaller or decreases in diameter.

Other objects will appear hereinafter.

DESCRIPTION OF FIGURES IN THE DRAWINGS FIG. 1 is an exploded perspectiveview of the webtension sensing means and the pneumatic sensing andcontrol unit which are embodied in the invention;

FIG. 2 is a side elevational view illustrating a feed roll and a take-uproll for a web of paper, plastic resinous film, or the like, having thenew web-tensioning apparatus applied thereto;

FIG. 3 is an elevational view of the parts of the invention shown inFIG. 2, as seen from the left hand side in FIG. 2;

FIG. 4 is an elevational view, partly in section, of the web-tensionsensing and control means embodied in the invention;

FIG. 5 is a view on line 5-5 in FIG. 4, partly in section and partly inelevation, illustrating parts of the web-tension sensing and controlmeans;

FIG. 6 is a view on line 66 in FIG. 4, partly in section and partly inelevation, showing parts of the control means for the web-tensionsensing means embodied in the invention;

FIG. 7 is a sectional detail view on line 77 in FIG.

FIG. 8 is a sectional detail view on line 8-8 in FIG. 6 illustratingparts of the control means for the webtension sensing means embodied inthe invention;

FIG. 9 is a sectional detail view on line 9-9 in FIG.

FIG. 10 is an elevational view illustrating the power transmission meansfor operating the air valve control means for the pneumatic brakingmeans for the web roll-supporting shaft;

FIG. 11 is a sectional detail view on line 11-11 in FIG. 10;

FIG. 12 is a sectional detail view on line 12-12 in FIG. 10;

FIG. 13 is a sectional detail view on line 13-13 in FIG. 10;

FIG. 14 is an elevational view of the pneumatic air control valve forthe braking means for the web feed roll supporting shaft;

FIG. 15 is a diagrammatic view of parts of the pneumatic air controlcircuit and the operating means for the air control valve for thebraking means embodied in the invention;

FIG. 16 is a perspective view of a modified form of the new web-tensionsensing and control apparatus;

FIG. 17 is a view partly in section and partly in elevation illustratingparts of the pneumatic sensing and control means embodied in themodified form of the invention illustrated in FIGS. 16 to 21, inclusive;

FIG. 18 is a view partly in section and partly in eleva tion and issimilar to FIG. 17 but showing certain of the parts in a differentposition;

FIG. 19 is a view similar to FIGS. 17 and 18, but showing parts of theweb-tension sensing and control unit in still another position;

FIG. 20 is an enlarged sectional view of the pneumatic sensing andcontrol unit embodied in the form of the invention illustrated in FIGS.16 to 21, inclusive; and

FIG. 21 is a view partly in section and partly in elevation showingparts of the motion-limiting means for the pneumatic sensing and controlunit embodied in the form of the invention illustrated in FIGS. 16 to21, inclusive.

DETAILED DESCRIPTION OF THE PREFERRED FORM OF THE INVENTION ILLUSTRATEDIN FIGS. 1 TO 15, INCLUSIVE The Web-Tension Sensing and Control Device(Figs. 1 to 8, Inclusive) A typical and preferred embodiment of theinvention is illustrated in FIGS. 1 to 15, inclusive, of the drawings,wherein it is generally indicated at 30, and comprises a portablepneumatic web-tension sensing and control unit, generally indicated at31 (FIG. 1) and which includes a portable housing in which majorcomponents of the web-tension sensing and control unit 31 are embodied.

The web-tension sensing and control 31 is disclosed in detail inapplicants US Pat. No. 3,759,457, granted Sept. 18, 1973 and entitledWeb-guiding Apparatus and Position-Sensing and Control Unit Therefor,"reference being had particularly to FIGS. 1, 4 to 15, inclusive, and 19and 20 of the drawings of said patent and those parts of thespecification relative thereto, all of which are by referenceincorporated herein and made a part hereof; the web-tension sensing andcontrol unit being adopted to be positioned at a suitable point adjacentto a roll of paper, plastic resinous film, or the like, as will bedescribed hereinafter.

A supporting frame is generally indicated at 32 and supports a feed roll33 for a web of paper, plastic resinous film, or the like, which isrotatably mounted on a roll-supporting shaft 34, which is journaled inbearings (not shown) which are mounted on upright parts 35-3- 6-37 ofthe supporting frame 32. A flexible web 38 of paper, plastic resinousfilm, or the like, is unwound from the feed roll 33 onto a take-up roll39 which is carried by a take-up roll shaft 40 which is rotatablyjournaled in upright supporting members 41 which are mounted on asupporting frame 42 (FIGS. 2 and 3).

The new web-tension sensing and control apparatus 30 includes aweb-tension sensing unit, generally indicated at 43, and which includesa plurality (shown in FIGS. 1 and 3) of web-tension sensing members inthe form of rollers 44 which ride and bear upon the upper surface of theweb 38. EAch of these web-tension sensing members or rollers 44 isrotatably mounted, as at 46, on the lower end portions of sensingrollersupporting arm 45, each of which is pivotally or rockably mountedon a horizontal rocker shaft 47 having end portions which are rotatablymounted in upright supports 36 which are mounted on the supporting frame32 (FIGS. 2, 3, 4 and 5). The sensing rollersupporting arms 45 aresecured to the horizontal rocker shaft 47 by clamping means in the formof clamping collars 49 and tension-adjusting counterbalancing weightmembers 51 are adjustably mounted on the roller supporting arms 45 foradjustable movement therealong.

The rocker shaft 47 has a bifurcated yoke 52 mounted on one end portionthereof (right hand end portion, FIGS. 1, 2, 4, 6 and 9) and this yoke52 has a cam roller 53 rotatably mounted thereon, as at 54, (FIGS. 1, 4and 6). The cam roller 53 rides on or against one lateral edge surface56 of an upright operating arm 55 which is pivotally mounted between itsends, as at 57, on one of the upright supporting members 36 (FIGS. 1, 6and 8). The lower end portion of the operating arm 55-56 is pivotallyconnected, as at 58, to one end portion 59 of a pneumatic sensing andcontrol arm 60 which is slidably guided over a supporting pin 69 whichis attached to one of the upright sup porting members 36 (FIG. 6 Theother end portion 61 of the pneumatic sensing arm 60 extends into thethroat 62 of a pneumatic sensing and control head 63 which forms part ofthe web-tension and sensing control unit 31 and which is described indetail in the applicants earlier US. Pat. No. 3,759,457 referred toabove. The operating arm 55 is normally urged, by a spring 65, againstthe cam roller 53; one end portion of the spring 65 being connected, asat 66, to an arm 67 on one of the upright supporting members 36 and theother end portion of the spring 65 being attached, as at 68, to thelower end portion of the operating arm 55 (FIGS. 2 and 6).

The Braking Means for the Web Roll-Supporting Shaft 34 (FIGS. 2 and 3)The braking means for the web roll-supporting shaft 34 (FIGS. 2 and 3)are generally indicated at 35 (FIGS. 2 and 3) and are associated withand are adapted to brake the rotation of the web roll-supporting shaft34 for the roll 33 of paper, flexible film, or the like.

The braking means 35 for the web roll-supporting shaft 34 may be of anysuitable pneumatically operated or other type but a suitable andpreferred braking device for this purpose is the pneumatically operateddiaphragm brake manufactured by the Horton Manufacturing Co., Inc. ofMinneapolis, Minnesota, and known as its Model K diaphragm brake. Asshown in FIGS. 2 and 3, two of these braking units 35 are employed inthe invention, one in association with each end portion of the webroll-supporting shaft 34, and they are mounted on the upright supportingmembers 36.

The Pneumatic Control Valve means for the Braking Means (FIGS. 10 to 14,Inclusive) The pneumatic braking units 35 for the web rollsupportingshaft 34 are under the control of an air valve which is generallyindicated at 50 (FIGS. 10, 13 and 14), and which may be of any suitabletype. However, a suitable air control valve 50 for the diaphragm brakingdevices 35 is a constant bleed regulator air valve manufactured by theBastion-Blessing Company of Chicago, Ill., and known as its Atinch Model8702PB, having a variable capacity of from 0 to I60 p.s.i.

It will be noted, by reference to FIGS. 13 and 14, that the air controlvalve 50 includes a generally cylindrical body 70 having an air inlet 71and air outlets 72 which are connected to the air inlets 73 of thediaphragm brake units 35 (FIGS. 2 and 3).

The Pneumatic Control and Operating Means For the Air Control Valve 50(FIGS. 10, 11, I2, 13 and IS) The pneumatic control means and theoperating means for the air control valve 50 are generally indicated at48 (FIGS. 10, ll, l2, l3 and 15), and are under the control ofthepneumatic web-tension sensing and control system 31 and the pneumaticsensing head 62 which is embodied therein, as will now be described.

As described in applicants US. Pat. No. 3,759,457 (FIGS. 19 and 20) thepneumatic sensing head 63 has a low pressure air supply line 74 which isconnected to a suitable source of compressed air 75, and the pneumaticsensing head 63 has a low pressure air outlet 76 which is connected to alow pressure air supply line 77 in which is arranged a three-waypilot-operated high pressure air flow control valve unit 78 which isnormally closed but is adapted to be opened by a supply of low pressureair from the pneumatic sensing head 63 by way of the low pressure airsupply line 77.

The pneumatic sensing head 63 has a second low pressure air supplyoutlet 79 which is connected to a second low pressure air supply line 80in which is arranged a second normally closed three-way pilotoperatedhigh pressure air valve 81. A high pressure air supply line 82 leadsfrom the normally closed high pressure air flow control valve 78 into ahydraulic reservoir 83 for oil or other fluid, and an oil line 84 leadsfrom the oil reservoir 83 to an oil flow control valve 85 which isconnected, by way of an oil line 86, to a hydraulic cylinder 87 at oneside of a piston 88 which is slidably mounted in the cylinder 87 (FIGS.10 and 15).

Similarly, the normally closed high pressure threeway pilot-operated airflow control valve 81 leads by way of a high pressure air supply line 89to a hydraulic reservoir 90 for oil or like hydraulic fluid and thehydraulic oil reservoir 90 leads by way of an oil supply line 91 to anoil flow control valve 92 which leads to the cylinder 87 at the oppositeside of the piston 88 (FIGS. 10 and 15).

The piston 88 is mounted on a piston rod 94 which has a lateralextension 95 which projects externally of the cylinder 87 and isslidably guided, as at 96, on a supporting frame 97 (FIGS. l0, l2 and15). The lateral extension 95 of the piston rod 94 is connected, as at98, by a connecting or tie bar member 99 to a slidable rack member 100which has a row of teeth 10] on its lower edge. The rack of teeth 101mesh with a spur gear 102 which is rotatably mounted on a shaft 103which is rotatably mounted on the supporting frame 97 and has a movablevalve body 105 of the air valve 50 mounted thereon (FIG. 13); the rackmember 100 being slidably mounted and guided on the supporting frame 97by brackets 104 (FIGS. and 12).

OPERATION OF THE PREFERRED FORM OF THE INVENTION ILLUSTRATED IN FIGS. 1to 15, INCLUSIVE When the web 38 is in proper tension and the tensionsensing arm 60-61 is in its normal position, as in FIG. 6, the highpressure air flow valve control valves 78 and 81 in the pneumaticsensing and control system 31, are closed so that air under highpressure is not supplied by way of either the two high pressure airsupply lines 82 and 89, respectively, to either of the hydrauliccylinders 83 and 90 for the hydraulic cylinder-piston power means87-94-95, with the result that the web tension sensing roller members 44and their supporting arms 45 and attached counterbalance members 51remain in their normal operating position relative to the web 31.

However, in the event that the web 38 from the roll 33 of paper, plasticresinous film, or like flexible sheet material looses tension or becomestoo slack, the counterweighted web tension sensing roller members 44 andtheir supporting shafts 45 and the counterbalance members 51 thereonwill pivot on the rocker shaft 47 (clockwise, FIGS. 1 and 5). Thismovement of the rocker shaft 47 causes the bifurcated yoke 52 and thecam roller 53 carried thereby to move away from the operating arm 55whereupon the spring 65 will cause the operating arm 55 to pivot, at 57,(clockwise, FIG. 6) and thereby withdraw the pneumatic sensing armmember 60-61 outwardly relative to the throat 62 in the body of thesensing head 63 (right to left, FIG. 6) from the position in which thepneumatic sensing arm member 60-61 is shown in FIG. 6.

When the pneumatic sensing arm 60-61 is thus moved outwardly relative tothe throat 62 in the pneumatic sensing head 63 (right to left, FIG. 6),a supply of air under relatively low pressure is allowed to flow in thepneumatic system 31, from the air reservoir 75 by way of the lowpressure air supply line 77 to the normally closed high pressurethree-way pilot-operated air control flow valve 78 through the highpressure air supply line 82 to the hydraulic cylinder 83, therebyforcing oil under pressure through the oil line 84-85-86 into thehydraulic cylinder 87 at one side of the piston 88 and thereby movingthe piston 88 and the piston rod 94-95 on which it is mounted (right toleft, as seen in FIG. This movement of the piston 88 and the piston rod94-95 acts, through the connecting or tie member 99, to move the rackmember 100-101 slidably in the same direction and this movement of therack member 100-101 acts, through the spur gear 102, to rotate the shaft103 on which the spur gear is mounted, and also to rotate the movablevalve member 105 on the shaft within the body of the air flow controlvalve 50, thereby allowing air to flow from the air valve 50 by way ofthe air lines 72 and the inlets 73 into the diaphragm braking units 35to brake the rotation of the web roll-supporting shaft 34 and the roll33 of paper, plastic resinous film, or the like, carried thereby, andthus taking up the slack in the web 38.

However, after the proper tension has thus been restored to the web 38,and the web 38 has been returned to its normal position, the movement ofthe web 38 back into its normal position raises the web-tension sensingroller members 44 which ride thereon and thus causes the web tensionsensing rollers 44 and their supporting shafts 45 and the counterbalancemembers 31 thereon to rotate on the rocker shaft 47 (counterclockwise,FIGS. 5 and 6). This movement of the rocker shaft 47 and the yoke 52thereon causes the cam roller 53 to be urged against the edge surface 56of the operating arm 55, thereby pivoting the operating arm 55, at 57,counterclockwise (FIG. 6). This movement of the operating arm 55 causesits lower end portion, through the pivotal connection 58, to move thepneumatic sensing arm 60-61 back into its normal position in andrelative to the throat 62 in the pneumatic sensing head 63 and into theposition in which the parts are shown in FIG. 6, thereby moving thepneumatic sensing arm 60-61 into position relative to the throat 62 andthe sensing head 63 to enable air under relatively low air pressure toflow through the sensing head 63 by way of the low pressure air outlet79 and the low pressure air line -81-89 into the hydraulic cylinder 90and thus cause oil to flow by way of the oil line 90-92-93 into thecylinder 87 at the opposite side (left hand side as seen in FIG. 15) ofthe piston 88. This movement of oil under pressure into the cylinder 87,by way of the oil line 90-92-93, causes the piston 88 and the piston rod94-95 to move back into their normal position (left to right in FIG. 15)into the position in which the parts are shown in FIG. 15 and thismovement of the piston rod 94-95 acts through the connecting or tiemember 99 to move the rack 100-101 in the same direction, and themovement thus imparted to the rack 100-101 acts, through the spur gear102, to rotate the shaft 103 and the movable operating valve member 105thereon back into their normal position, thus cutting off the supply ofair through the air control valve unit 50 to the diaphragm brakingdevices 35 and thus releasing the braking action on the roll supportingshaft 34 which then becomes free to rotate at its normal predeterminedspeed to correspond with the desired movement of the web roll 33.

The air flow control valve unit 50 for the diaphragm braking units 35,as pointed out above, has a variable capacity from O to I60 p.s.i. but apreferred normal operating range is from O to 20 p.s.i.

DESCRIPTION OF THE CONSTRUCTION OF THE MODIFIED FORM OF THE INVENTIONILLUSTRATED IN FIGS. 16 TO 21, INCLUSIVE A modified form ofa web tensionsensing and control device for use in the invention is illustrated inFIGS. 16 to 21, inclusive, where it is generally indicated at 106, andcomprises a web tension sensing roll 107 having a trunnion 108 at oneend which is rotatably mounted in a supporting arm member 109 which ispivotally mounted, as at 110, in an upright supporting member 111 whichis mounted on a supporting frame 112. The web-tension sensing roll 107has a second trunnion 113 at its opposite end which is rotatably mountedin a pneumatic web tension sensing member 114 which is pivotally mountedon a shaft 115 which is attached to an upright supporting bracket 116which is carried by a supporting frame 116 (FIGS. 16 and 17).

The pneumatic web tension sensing arm 114 has an L-shaped pneumaticweb-tension sensing member 118 mounted on one side 119 thereof and thispneumatic web-tension sensing member 118 has a laterally projecting arm120 which projects into the throat 62a in the sensing head 63a whichcorresponds in structure and in function to the sensing head 63 in thepreferred form of the invention shown in FIGS. 1 to 15, inclusive.

The modified form of the invention illustrated in FIGS. 16 to 21,inclusive. embodies a motion-limiting device in the form ofa dash potunit which is generally indicated at 121 and includes a dash potcylinder 122 which has a curved body portion 123 at one end thereof andthis curved body portion 123 of the dash pot cylinder 122 is mounted, bymeans of a supporting rod member 124, on an upright support 125 which ismounted on the supporting member 117 (FIG. 16).

The dash pot cylinder 122 has a coil spring 126 therein which bearsagainst a piston 127 which is connected to a piston rod 128 whichprojects externallly of the dash pot cylinder 122 and has an end portion129 which is connected to a member 130 which is mounted on a shaft 131which is rotatably mounted in the lower end portion of the pneumaticsensing arm 114 (FIGS. 16 and 21).

DESCRIPTION OF THE OPERATION OF THE MODIFIED FORM OF THE INVENTIONILLUSTRATED IN FIGS. 16 TO 21, INCLUSIVE As shown in FIGS. 16 to 20,inclusive, the web tension sensing roll or cylinder 107 normally rideson the web 380 of paper, plastic resinous film, or the like, which maybe fed from a roll of the same, such as the web roll 33 in the preferredform of the invention shown in FIGS. 1 to 15, inclusive, and when theweb 38a is under proper tension the pneumatic web tension sensing unit114-118-120 is disposed, with respect to the pneumatic sensing head 63a,and the throat 62a therein, in the normal position in which the partsare shown in FIG. 17, so that the pneumatic control means and the powermeans and the power transmission means for operating the air conttrolvalve 50 for the diaphragm braking units 35, will be disposed in theirposition to maintain the diaphragm braking units 35 in their normalposition with respect to the web roll supporting shaft, such as 34, withwhich they are associated.

However, when the web tension sensing roll 107 senses a slack conditionin the web 38a it will pivot on its supporting trunnions 108 and 113 ina direction to move the pneumatic web tension-sensing unit 114-11- 8-120into position relative to the sensing head 63a and its throat 620, asshown in FIG. 19, thereby enabling the pneumatic sensing head 63a toactuate the pneumatic control system 31 in such a manner as to allow airunder relatively low air pressure to flow through the sensing head 630by way of the low pressure air supply line 77 to the normally closedhigh pressure pilotoperated air valve 78 to allow air under highpressure to flow, by way of the high air pressure line 82 into thehydraulic cylinder 83 and thus allow oil from the hydraulic cylinder 83to flow through the oil line 84-8- -86 into the cylinder 87 at one sideof the piston 88, thereby moving the piston rod 94-95 and the rack100-101 attached thereto, in a direction (right to left, FIGS. 10 and torotate the spur gear 102 and the valve operating shaft 103 into aposition to open the air flow control valve 50 and thus allow, air toflow by way of the lines 72-73-72-73 to the pneumatic diaphragm brakingunits 35 and thus brake the action of the web roll supporting shaft, as34.

However, when the web tension sensing roller 107 senses a taut conditionin the web 38a it will pivot on its supporting trunnions 108-113 into aposition to move the pneumatic sensing unit 114-118-120 relative to thesensing head 63a and its throat 62a into the position in which the partsare shown in FIG. 18, thereby allowing air under relatively low pressureto flow through the sensing head 63a by way of the low pressure airsupply line to the normally closed three-way pilot-operated highpressure air valve 81, to open the latter and thus allow air under highpressure to flow into the hydraulic cylinder to force oil therefrom byway of the line 91-92-93 into the cylinder 87 at the opposite side ofthe piston 88 (left side, FIG. 15), and thereby move the piston rod94-95 and its attached rack -101 (left to right, FIG. 15) relative tothe cylinder 87. This movement of the rack 100-101 causes the rack100-101 to rotate the spur gear 102 and the valve-operating shaft 103 ina direction to cut off the flow of air through the air control valve 50to the diaphragm braking units 35 and thus relieve the braking action onthe web roll supporting shaft, as 34.

In the use of the form of the invention illustrated in FIGS. 16 to 21,inclusive, the motion limiting or dash pot device illustrated in FIGS.16 to 19, inclusive, acts by way of the spring 126, piston 127, pistonrod 128 and parts 129-131, to return the pneumatic sensing unit114-118-120 to its normal position, as in FIG. 16, after each operationthereof.

It will thus be seen from the foregoing description. considered inconjunction with the accompanying drawings, that the present inventionprovides a new and improved web tension device having the desirableadvantages and characteristics and accomplishing its in tended objectsincluding those hereinbefore pointed out and others which are inherentin the invention.

We claim:

1. A web tension sensing and control apparatus for sensing andcontrolling the tension of a web of paper, plastic resinous film, or thelike, fed from a roll thereof carried by a roll-supporting shaft,comprising:

a. supporting means;

I). web-tension sensing means movably mounted on the said supportingmeans and adapted to bear upon the said web above the latter;

c. pneumatically operated braking means on the said roll-supportingshaft for braking the action of said roll-supporting shaft;

d. air supply means for supplying air under pressure to the saidpneumatically operated braking means;

e. first air valve control means for controlling the flow of air to saidpneumatically operated braking means to actuate the latter;

f. power means for operating the said first air valve control means;

g. pneumatically controlled power transmission means for operating thesaid power means;

h. pneumatic control means under the control of the said web-tensionsensing means for controlling the operation of the said pneumaticallycontrolled power transmission means and including 1 a pneumatic sensinghead having therein (a) a throat portion;

2 a sensing member operable by and responsive to movement of the saidweb-tension-sensing means and having a portion movable into and out ofthe said throat portion of the said pneumatic sensing head; and

3 second air valve control means under the control of the said pneumaticsensing head and the said throat portion thereof and the said portion ofthe said sensing member and responsive to the position of the saidportion of the said sensing member in and relative to the said throatportion of the said pneumatic sensing head for controlling the operationof the said pneumatically controlled power transmission means.

2. A web tension sensing and control apparatus as defined in claim 1 inwhich the said pneumatic control means is in the form of a portable unitadapted to be disposed adjacent said web and in which the said portableunit includes flexible air conducting lines interconnecting the saidpneumatic control means and the said second air valve control means.

3. A web tension sensing and control apparatus as defined in claim 1 inwhich the said web tension sensing means includes a a plurality ofweb-tension sensing members adapted to ride upon the said web andarranged in spaced relationship transversely of the said web above thelatter; and

b means for rotatably mounting the said web-tension sensing rollers inspaced relationship above the said web.

4. A web tension sensing and control apparatus as defined in claim 1 inwhich a the said web-tension sensing means is in the form 5. A webtension sensing and control apparatus as defined in claim 1 in which athe said pneumatic sensing head is in the form of a portable unitadapted to be positioned at a selected point adjacent the said web.

1. A web tension sensing and control apparatus for sensing andcontrolling the tension of a web of paper, plastic resinous film, or thelike, fed from a roll thereof carried by a roll-supporting shaft,comprising: a. supporting means; b. web-tension sensing means movablymounted on the said supporting means and adapted to bear upon the saidweb above the latter; c. pneumatically operated braking means on thesaid rollsupporting shaft for braking the action of said roll-supportingshaft; d. air supply means for supplying air under pressure to the saidpneumatically operated braking means; e. first air valve control meansfor controlling the flow of air to said pneumatically operated brakingmeans to actuate the latter; f. power means for operating the said firstair valve control means; g. pneumatically controlled power transmissionmeans for operating the said power means; h. pneumatic control meansunder the control of the said webtension sensing means for controllingthe operation of the said pneumatically controlled power transmissionmeans and including 1 a pneumatic sensing head having therein (a) athroat portion; 2 a sensing member operable by and responsive tomovement of the said web-tension-sensing means and having a portionmovable into and out of the said throat portion of the said pneumaticsensing head; and 3 second air valve control means under the control ofthe said pneumatic sensing head and the said throat portion thereof andthe said portion of the said sensing member and responsive to theposition of the said portion of the said sensing member in and relativeto the said throat portion of the said pneumatic sensing head forcontrolling the operation of the said pneumatically controlled powertransmission means.
 2. A web tension sensing and control apparatus asdefined in claim 1 in which the saId pneumatic control means is in theform of a portable unit adapted to be disposed adjacent said web and inwhich the said portable unit includes flexible air conducting linesinterconnecting the said pneumatic control means and the said second airvalve control means.
 3. A web tension sensing and control apparatus asdefined in claim 1 in which the said web tension sensing means includesa a plurality of web-tension sensing members adapted to ride upon thesaid web and arranged in spaced relationship transversely of the saidweb above the latter; and b means for rotatably mounting the saidweb-tension sensing rollers in spaced relationship above the said web.4. A web tension sensing and control apparatus as defined in claim 1 inwhich a the said web-tension sensing means is in the form of a singlecylindrical web tension sensing roller member rotatably mounted on thesaid supporting means and adapted to bear upon the said web above thelatter.
 5. A web tension sensing and control apparatus as defined inclaim 1 in which a the said pneumatic sensing head is in the form of aportable unit adapted to be positioned at a selected point adjacent thesaid web.